Could you tell me what happens if a person who is not actually having a stroke is given tpa (alteplase)?

Increased bleed risk: Tissue plasminogen activator, or tpa, (alteplase) "dissolves" clots, so the main risk from it's administration is an increased risk of bleeding. One way to reduce the risk is to have strict rules on who it is administered to, based on many factors including time since symptoms began. Another is to administer it right where it is needed, near the location of the artery which contains the clot.